Alzheimer's disease (“AD”) is a neurodegenerative illness characterized by memory loss and other cognitive deficits. AD is the most common form of dementia and affects one in every eight people over the age of 65 and one in every two over the age of 85. AD is the sixth leading cause of death in the United States. Over 5.5 million Americans suffer from AD, with an estimated annual cost of $200 billion USD. By 2050, it is projected that AD will affect over 20 million Americans at an annual price tag of $1.1 Trillion USD (in 2011 dollars). Around the world, the estimated figures for the year 2011 were over 37 million sufferers, at an associated cost of over $600 billion (USD).
A significant hindrance to identification and treatment of AD is the paucity of effective diagnostic tests. At present, AD is typically only conclusively diagnosed by post-mortem histopathological analysis. Diagnosis in living patients relies primarily on psychiatric testing to detect cognitive impairment. However, the major neuropathological hallmarks of AD—extracellular amyloid-β (“Aβ”) plaque deposits and intracellular neurofibrillary tangles—manifest long before clinical symptoms are discernable. Aβ deposits also represent a major risk factor for hemorrhagic stroke.
Thus, a need exists for compositions and methods suitable for in vivo imaging of intracranial Aβ plaque deposits, for diagnostic purposes and to monitor the effectiveness of therapies targeted at preventing Aβ plaque deposits. Current approaches suffer from one or more of a myriad of drawbacks, including invasiveness, lack of specificity of the imaging agents for Aβ deposits, unsuitable resolution, the inability of the imaging agents to cross the blood-brain barrier (“BBB”) effectively, a tendency on the part of the imaging agents to induce an unsuitably high pro-inflammatory response in the vicinity of the Aβ deposits, and unsuitable cytotoxicity. Thus, a further need exists for compositions and methods that are suitable for in vivo imaging of intracranial Aβ plaque deposits, but that do not suffer from one or more of the drawbacks of current approaches. A still further need exists for compositions and methods suitable to treat or aid treatment or prophylaxis of AD.